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Cubic AlGaN/GaN Hetero-Field Effect Transistors with Normally On and Normally Off Operation

Published online by Cambridge University Press:  31 January 2011

Donat J. As ,
Elena Tschumak ,
Florentina Niebelschüetz ,
W. Jatal ,
Joerg Pezoldt ,
Ralf Granzner ,
Frank Schwierz  and
Klaus Lischka
Donat J. As
Affiliation:
d.as@uni-paderborn.de, University of Paderborn, Department of Physics, Paderborn, Germany
Elena Tschumak
Affiliation:
elena.tschumak@uni-paderborn.de, University of Paderborn, Department of Physics, Paderborn, NRW, Germany
Florentina Niebelschüetz
Affiliation:
florentina.niebelschuetz@tu-ilmenau.de, TU Ilmenau, FG Nanotechnologie, Ilmenau, Thueringen, Germany
W. Jatal
Affiliation:
w.jatal@tu-ilmenau.de, TU Ilmenau, FG Nanotechnologie, Ilmenau, Thueringen, Germany
Joerg Pezoldt
Affiliation:
joerg.pezoldt@tu-ilmenau.de, TU Ilmenau, FG Nanotechnologie, Ilmenau, Thueringen, Germany
Ralf Granzner
Affiliation:
ralf.granzner@tu-ilmenau.de, TU Ilmenau, FG Festkörperelektronik, Ilmenau, Thueringen, Germany
Frank Schwierz
Affiliation:
frank.schwierz@tu-ilmenau.de, TU Ilmenau, FG Festkörperelektronik, Ilmenau, Thueringen, Germany
Klaus Lischka
Affiliation:
lischka@upb.de, University of Paderborn, Department of Physics, Paderborn, NRW, Germany
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Abstract

Non-polar cubic AlGaN/GaN HFETs were grown by plasma assisted MBE on 3C-SiC substrates. Both normally-on and normally-off HFETs were fabricated using contact lithography. Our devices have a gate length of 2 μm, a gate width of 25 μm, and source-to-drain spacing of 8 μm. For the source and drain contacts the Al0.36Ga0.64N top layer was removed by reactive ion etching (RIE) with SiCl4 and Ti/Al/Ni/Au ohmic contacts were thermally evaporated. The gate metal was Pd/Ni/Au. At room temperature the DC-characteristics clearly demonstrate enhancement and depletion mode operation with threshold voltages of +0.7 V and −8.0 V, respectively. A transconductance of about 5 mS/mm was measured at a drain source voltage of 10 V for our cubic AlGaN/GaN HFETs, which is comparable to that observed in non-polar a-plane devices. From capacity voltage measurements a 2D carrier concentration of about 7×1012 cm-2 is estimated. The influence of source and drain contact resistance, leakage current through the gate contact and parallel conductivity in the underlaying GaN buffer are discussed.

Keywords

nitridemolecular beam epitaxy (MBE)devices
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1202: Symposium I – III-Nitride Materials for Sensing, Energy Conversion and Controlled Light-Matter Interactions , 2009 , 1202-I04-08
Copyright
Copyright © Materials Research Society 2010

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